Revealing the Indispensable Role of the RFamide Functionality using a Novel Acid Labile Benzofuranone based Amine (ALBA) Linker

Abstract

The RFamide family of peptides represents an important class of GPCR ligand neuropeptides covering a wide range of biological functions. While many analogues of the highly conserved C‐terminal RFamide motif within this peptide class have been synthesized and their functional significance elucidated, additional exploration of the structure activity relationship is of value. We have developed a novel linker for solid phase peptide synthesis (SPPS) which is able to anchor amine functionalised compounds for further elaboration. The acid labile benzofuranone based amine (ALBA) linker (5‐(3‐aminopropylcarbamoyl)‐2‐[[tert‐butyl(diphenyl)silyl]oxymethyl]benzoic acid) is compatible with Fmoc based SPPS and has two cleavage modes. As a proof of concept, the ALBA linker was used to successfully synthesise a novel analogue of Kisspeptin 10, the natural ligand for GPCR54, whereby the natural RFamide motif was replaced with an RFamine. Biological evaluation of the amine‐containing analogue revealed that the group is not compatible with receptor activation.